The present invention relates to a fuel injector and an internal combustion engine having a fuel injector and, in particularly to a fuel injector in which a fuel spray having a superior ignitability and a superior combustibility is formed and an internal combustion engine having a fuel injector.
The present invention relates a fuel injector for forming a complex fuel spray having a superior ignitability and a superior combustibility and an internal combustion engine having a fuel injector.
An inlet pipe fuel injection device has known, in such a fuel injection device the fuel is injected into an inlet pipe of an internal combustion engine and in addition to the above stated inlet pipe fuel injection device a direct fuel injection device has known, in such a fuel injection device the fuel is injected directly into a combustion chamber (a cylinder). Such a latter stated conventional direct fuel injection device is disclosed in, for example, Japanese patent laid-open publication No. Hei 5-33,739.
As disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, it is difficult to mix homogeneously the fuel which has injected directly to the combustion chamber with the inhale air in the combustion chamber. Therefore, it is important to produce a promotion for atomizing the fuel which has injected directly to the combustion chamber.
To atomize the fuel, up to now an impartment of a swirling force with the fuel which is injected from a fuel injector has carried out. As shown in the above stated Japanese patent laid-open publication No. Hei-5 33,739, the direct fuel injection device having a means for imparting the swirling force against the fuel is disclosed.
Herein, the direct fuel injection device shown in the above stated Japanese patent laid-open publication No. Hei-5 33,739, the direct fuel injection device comprises an injection nozzle for injecting the fuel from an injection hole, a cylindrical shape cover having a bottom portion for constituting an air chamber at an outer side of the injection nozzle, a swirl chamber which is formed at a side of the bottom portion of the cover to communicate to the injection hole of the injection nozzle, and a check valve body which opens and closes the injection hole.
With the above stated conventional direct fuel injection device structure, the swirl chamber has an injection hole and this injection hole introduces the assist air from a tangential direction directing for an inner peripheral face of the swirl chamber from the air chamber which is constituted the cylindrical shape cover having the bottom portion. In accordance with the above stated assist air which is injected from the injection hole of the swirl chamber, the fuel for injecting to the injection hole of the injection nozzle can be imparted the swirl force.
Further, the injection hole and a passage for introducing the assist air from the air chamber to the swirl chamber are provided with two stages structure, namely the injection hole and the passage of the swirl chamber are provided at an upper direction and a lower direction (an axial direction of the check valve body) or an upstream side and at a downstream side of the check valve body. Each of the injection hole and the passage of the swirl chamber at the upper direction and the lower direction have the same structure.
However, in the above stated conventional direct fuel injection device, the check valve is arranged at a discharge side. Further, the swirl force impartment means is provided at a downstream side of a metering portion of the fuel but is not provided at an upstream side of the metering portion of the fuel.
As a result, after the fuel passes through the metering portion of the fuel without the impartment of the swirl force, the fuel is imparted first the swirl force at the downstream side of the metering portion of the fuel, namely the swirl force is imparted first the swirl force in the swirl chamber according to the assist air.
Accordingly, in the conventional direct fuel injection device structure shown in the above stated Japanese patent laid-open publication No. Hei-5 33,739, there is no idea about the impartment of the swirl force with the fuel using a fuel passage at the upstream of the metering portion of a valve body.
In the conventional technique including the above stated direct fuel injection device, it has promoted the atomization for the fuel and it has devised about spray direction of the fuel and a spreading of the fuel spray. However, as stated in hereinafter, there is not taken fully a consideration with respect to a spray shape of the fuel, a spray diameter of the fuel and a spray structure of the fuel in which both of the ignitability (a spark-in property) and the combustibility (a propagation of fire) are improved compatibly.
To attain the optimum property for the spray of the fuel which is injected from the fuel injector, it is necessary to consider at least following three characteristics.
First of all, the first characteristic is the fuel spray shape and factors for this fuel spray shape are a spreading angle and a reaching distance of the fuel. The second characteristic is a size of the spray fuel particle and it is necessary to lessen a number of a large spray fuel particle size as possible and to make an uniformity of a spray fuel particle size distribution. The third characteristic is a spray structure of the fuel and it is necessary to suit properly a spatial distribution of the fuel particle to be sprayed.
The inventors of the present invention have studied about the various experimentation analyses in which how these fuel spray characteristics relate to the combustion properties in the internal combustion engine.
As the results of the studies, they found out following facts, that is in a case where by making large the spreading angle of the spray of the fuel an inertia force of the fuel spray is made weak and then the reaching distance of the fuel spray is made short, it is effective to obtain the stability of the combustion. Further, on the other hand, by making small the spreading angle of the spray of the fuel the inertia force of the fuel spray is made strong and then the mixture air having a superior ignitability is generated, but it was ascertained clearly that it has a tendency in which the unburned gas components (HC, CO) of the fuel increase, etc.